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Radeon ROCm 4.1 Released - Still Without RDNA GPU Support

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  • #51
    Originally posted by skeevy420 View Post
    For all intents and purposes, CDNA is basically headless RDNA; both are the successor to GCN.

    https://www.amd.com/system/files/doc...whitepaper.pdf

    The classic GCN compute cores contain a variety of pipelines optimized for scalar and vector instructions. In particular, each CU contains
    a scalar register file, a scalar execution unit, and a scalar data cache to handle instructions that are shared across the wavefront, such as
    common control logic or address calculations. Similarly, the CUs also contain four large vector register files, four vector execution units that
    are optimized for FP32, and a vector data cache. Generally, the vector pipelines are 16-wide and each 64-wide wavefront is executed over
    four cycles.
    The AMD CDNA architecture builds on GCN’s foundation of scalars and vectors and adds matrices as a first class citizen while
    simultaneously adding support for new numerical formats for machine learning and preserving backwards compatibility for any software written for the GCN architecture.
    These Matrix Core Engines add a new family of wavefront-level instructions, the Matrix Fused Multiply-
    Add or MFMA. The MFMA family performs mixed-precision arithmetic and operates on KxN matrices using four different types of input
    data: 8-bit integers (INT8), 16-bit half-precision FP (FP16), 16-bit brain FP (bf16), and 32-bit single-precision (FP32). All MFMA instructions
    produce either 32-bit integer (INT32) or FP32 output, which reduces the likelihood of overflowing during the final accumulation stages of a
    matrix multiplication.

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    • #52
      Originally posted by bridgman View Post

      Yep... the message is a bit misleading though... what it is supposed to be saying is "you can't run 4.1 userspace without the 4.1 kernel driver".

      The required kernel driver changes are on their way upstream but not there yet AFAIK, so just going to newer kernel isn't going to help. I was going to say "if you can go back to 4.0 userspace in the short term that would probably be best" but you already said that you had problems with 4.0. Do you happen to remember what problems you saw ?
      The problem was rocminfo listed and stated both GPU's and cpu fine. But when something like [email protected], luxmark ect tried to use any GPU it failed on both GPU's
      CPU worked fine.

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      • #53
        From the same paper:

        Unlike the graphics-oriented AMD RDNA™ family, the AMD CDNA family removes all of the fixed-function hardware that is designed to accelerate graphics tasks such as rasterization, tessellation, graphics caches, blending, and even the display engine
        Or Headless RDNA.

        From the RDNA whitepaper:

        The new RDNA architecture is optimized for efficiency and programmability while offering backwards compatibility with the GCN architecture. It still uses the same seven basic instruction types: scalar compute, scalar memory, vector compute, vector memory, branches, export, and messages. However, the new architecture fundamentally reorganizes the data flow within the processor, boosting performance and improving efficiency.
        Both are an evolution of GCN and the biggest difference between the two is one is designed for graphics output and the other is designed for computing. Laymanized -- headless and not headless.

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        • #54
          Originally posted by skeevy420 View Post
          Both are an evolution of GCN and the biggest difference between the two is one is designed for graphics output and the other is designed for computing. Laymanized -- headless and not headless.
          Mind if I tweak this a bit ? I think it's important to distinguish between "no display connector" (with or without display HW) and "no graphics pipeline".

          We do sell a lot of headless graphics cards for remote gaming and virtual desktop applications, while the compute cards are unable to do graphics even remotely.

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          • #55
            Originally posted by bridgman View Post

            Mind if I tweak this a bit ? I think it's important to distinguish between "no display connector" (with or without display HW) and "no graphics pipeline".

            We do sell a lot of headless graphics cards for remote gaming and virtual desktop applications, while the compute cards are unable to do graphics even remotely.
            I was wondering how a CDNA would work with DRI_PRIME=1 so I guess that answers that. I guess I won't be buying those used to supplement desktop APUs

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            • #56
              Originally posted by skeevy420 View Post
              I was wondering how a CDNA would work with DRI_PRIME=1 so I guess that answers that. I guess I won't be buying those used to supplement desktop APUs
              Yeah, they would not be good for supplementing APU graphics, although they would be really good for supplementing APU compute.
              Last edited by bridgman; 25 March 2021, 01:16 PM.

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              • #57
                Nice if they can give us a "prosumer" CDNA card that doesn't cost 5 grand but still gives us decent compute.

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                • #58
                  Originally posted by vegabook View Post
                  Nice if they can give us a "prosumer" CDNA card that doesn't cost 5 grand but still gives us decent compute.
                  as soon as they have chiplet design they can easily do this.
                  imagine a full version has 4 chips so they cut out 3 chips and you get a card for like the 1/4 of the price.

                  best case szenario for consumers would be a RDNA/CDNA chiplet design hybrid...
                  it is not technically impossible to build this.

                  some people claim it makes no sense to split GCN into RDNA and CDNA if you put these 2 chips together in a chiplet design hybried of RDNA+CDNA...

                  but i think they are wrong because General Compute if you care about performance is death and more specialized chips will rule the performance.

                  Phantom circuit Sequence Reducer Dyslexia

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